Herbarium, Museum of Biological Diversity. The Ohio State University.
Research interests are in classification and evolution of flowering plants, especially Compositae in Mexico and in temperate floras of southern South America. Investigations have also focused on island biology, especially anagenetic speciation in Ullung Island, Korea, and patterns, processes, and historical influences on populational differentiation and speciation in the Juan Fernández (Robinson Crusoe) Archipelago, Chile. A further interest is on the conceptual history of botanical classification.